CCI-779 is an anti-cancer agent with demonstrated significant inhibitory effects on tumor growth in a number of in vitro and in vivo models. Mechanistically, CCI-779 has been shown to inhibit kinase activity of mTOR (mammalian target of rapamycin), a key protein of phosphoinositide (PI) 3-kinase signal transduction. Inhibition leads to arrest of cells in the G1 phase of the cell cycle; an effect thought to delay the time to tumor progression or time to tumor recurrence. CCI-779 is currently undergoing clinical evaluation to treat patients with renal cell carcinoma (RCC).